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Old 07-14-2014, 04:25 AM   #1
CheaterPY
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Default Pan missfing under load

Hello gentlemen,

After several weeks of tuning my Pan, I still got the missfiring problem under load.

The bike ran like a champ for two years without any trouble and then started to lightly missfire on the highway.

I have changed the point (I have tested 2 new ones), condenser and weight springs of my ignition system, which as been just fine for 100 miles. Then it's been worst and worst with more and more missfirings and backfires.

I then have changed the coil (teste three differents units), plugs, plugs wires, I have tested for inteake leaks, I have tested the battery, checked the push rods. But nothing cured the missfiring.

The only trick is when I clean and sand the points, the bike runs perfect for 10 miles and it's back to the mad swinging machine. The bike is also runing good at low rpm and start on first kick even cold or hot.

What am I missing ?

Thanks ind avance for your thought
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Old 07-14-2014, 04:51 AM   #2
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Default Re: Pan missfing under load

Try running a wire from the motor to the ground on the battery. And make sure that your ignition system is grounded.
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Old 07-14-2014, 04:57 AM   #3
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Default Re: Pan missfing under load

Sounds like it may be the wrong ohm coil. If you are running points, you need the 5 ohm coil. If you have the 3 ohm one, it will burn up the points, and after you clean the burning/arc off the contacts, it runs until it overheats them again. Eventually, it will melt them, or turn the arms blue from heat. Not to mention, allowing the arm to bend, causing the points to be to wide. That is, if this is the real problem.

To eliminate the motor as the problem, do a leakdown test cold, and then hot. It could be a slightly sticking valve. If it pops out the intake, or exhaust, will tell you which one to inspect, if necessary. But my money is on the wrong coil.
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Old 07-14-2014, 08:12 AM   #4
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Default Re: Pan missfing under load

Thanks for the input guy.

The new coil is 12v 4.8 ohm dual fire from Andrews and I have also try to ride again with the old coil which worked fine for years ... the missfiring is the same.

I don't really get the trick with a wire from the motor to the ground on the battery ? Isn't the motor grounded by the frame ?
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Old 07-14-2014, 10:14 AM   #5
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Default Re: Pan missfing under load

Run a bypass wire around keyswitch then kill switch to see if either is malfunctioning. Batt ground trick works for charging issues too when wire run from regulator/rectifier mounting bolt to batt ground.
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Old 07-14-2014, 10:31 AM   #6
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Default Re: Pan missfing under load

Any chance your points plate screws or the screw that sets the points loosening for some reason?

You also say you switched to new points, yet you are sanding them? Why?
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Old 07-14-2014, 10:37 AM   #7
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Default Re: Pan missfing under load

Are you by chance running an aftermarket tach, I had a similar problem on my shovel, found out that the tach was shorting out, unhooked tach, problem solved.
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Old 07-14-2014, 10:55 AM   #8
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Default Re: Pan missfing under load

I have already bypassed the switch to test it, with no better results.

No charging issue, I have a charging light which is working fine.

Points are in place and the gap is good, I have tested from 0.018 to 0.022 with no results. The screw is solid.

I have tested the new points with some grease provided, worked fine until I twisted the thorttle more seriously. Then I cleaned and sanded, works perfect for 10 miles.

I don't have any tach at all

Thanks guys for your help so far
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Old 07-14-2014, 11:05 AM   #9
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Default Re: Pan missfing under load

is the wiring to the coil right ? correct polarity ? it will run reversed but will eat up the points.
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Old 07-14-2014, 12:19 PM   #10
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Default Re: Pan missfing under load

drain the gas and put new in... ya could have a shit batch of fuel.....
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Old 07-14-2014, 12:21 PM   #11
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Default Re: Pan missfing under load

Do you have slop in the shaft on your timer ?
that will cause erratic timing firing and cause the bike to run rough
so will a loose plate under your timer cover

give those a check
I had a knucklehead one time drive me crazy trying to find a rough running problem under load and that turned out to be the problem

also check for a loose wire in the timer as well
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Old 07-14-2014, 12:24 PM   #12
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Default Re: Pan missfing under load

under load I had the same issue.... had an air leak in the manifold
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Old 07-14-2014, 02:28 PM   #13
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Default Re: Pan missfing under load

draining gas has been my first idea ... Shaft of the timer is solid everything un timer work
fine. There are no + or - on the coil and has been wired the same way than my old one only one way to fix it on the bike ... Tonight I have been able to retorque the two manifold clamp and the missfiring was lightly better ... I will change the gaskets and will share the result

Thanks for the help
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Old 07-14-2014, 02:55 PM   #14
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Default Re: Pan missfing under load

Quote:
Originally Posted by CheaterPY View Post
Tonight I have been able to retorque the two manifold clamp and the missfiring was lightly better ... I will change the gaskets and will share the result
Make sure you pressure test the intake.
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Old 07-14-2014, 06:01 PM   #15
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Default Re: Pan missfing under load

Have you tried a new condenser?
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Old 07-14-2014, 06:24 PM   #16
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Default Re: Pan missfing under load

I like simple problem solving.

Let me say this, I am a fabricator with a limited amount of motorcycle engine tuning experience.

The intake leak suggestion is the first thing I would go for after verifying the ignition system. I would also check my valve lash too. If that fails, it's time to consider a compression leak down test to check the condition of your valves and rings.
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Old 07-15-2014, 01:10 AM   #17
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Default Re: Pan missfing under load

Have you checked your generator???

What kind of voltage regulator setup do you have?

Old style? last time polarized?


Quote:
Originally Posted by CheaterPY View Post
Hello gentlemen,

After several weeks of tuning my Pan, I still got the missfiring problem under load.

The bike ran like a champ for two years without any trouble and then started to lightly missfire on the highway.

I have changed the point (I have tested 2 new ones), condenser and weight springs of my ignition system, which as been just fine for 100 miles. Then it's been worst and worst with more and more missfirings and backfires.

I then have changed the coil (teste three differents units), plugs, plugs wires, I have tested for inteake leaks, I have tested the battery, checked the push rods. But nothing cured the missfiring.

The only trick is when I clean and sand the points, the bike runs perfect for 10 miles and it's back to the mad swinging machine. The bike is also runing good at low rpm and start on first kick even cold or hot.

What am I missing ?

Thanks ind avance for your thought
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Old 07-15-2014, 07:22 AM   #18
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Default Re: Pan missfing under load

For years, I checked intake leaks with starting fluid sprayed on the intake until I joined this form. I cant remember who it was now but, someone on here posted a pic of a plate he built with a air chuck in the middle that he bolted in place of the carb and shot low pressure air in the intake to check of intake leaks, I thought and still think it is genius. I took that idea one step farther and took a rubber freeze plug, removed the bolt and washers and glued a air chuck in it. Now I pull the breather off, wedge the freeze plug into the carb and can check the carb, gasket between carb and intake and intake to heads, this has sure made my life easier.

Something else to check, you said it pops while rolling on the throttle and that you changed out the points and springs but, did you check for loose or worn pivot posts for the weights. The slightest snag on these will drive a man bat shit crazy trying to track down a miss.
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Old 07-15-2014, 10:07 AM   #19
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Default Re: Pan missfing under load

Quote:
Originally Posted by CheaterPY View Post
Then I cleaned and sanded, works perfect for 10 miles.
You have bad or wrong condenser [Burning the points is a symptom of this] and also maybe wrong or wired wrong coil. This can be checked with a pencil by pulling a plug wire while running and arcing to the top of the plug and putting the pencils lead into the arc it should make a flare towards the plug if it flares to the wire it is wired backwards.
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Old 07-15-2014, 10:28 AM   #20
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Default Re: Pan missfing under load

Thanks a lot for all your inputs. I have a cycle electric generator
and a light for the check. The weights of the ignition systems are working fine and I can't see any play or worn pivot. I have tested two differents condensers and the missfiring is the same. I was focused on the standing and clearing points but this made the bike get cooler and I think that made the intake leak less important when the engine is cold ... I still need to check the pressure but I have to make the tool to check first. Thanks again everybody !
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